Abstract
The deposition of Mn atoms onto the $\mathrm{Si}(001)\text{\ensuremath{-}}(2\ifmmode\times\else\texttimes\fi{}1)$ reconstructed surface has been studied using scanning tunneling microscopy (STM) and first-principles electronic structure calculations. Room-temperature deposition of 0.1 ML (monolayer) of Mn gives rise to a disordered surface structure. After in situ annealing between 300 and $700\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, most of the Mn is incorporated into three-dimensional manganese silicide islands, and Si dimer rows reappear in the STM images on most of the substrate surface. At the same time, rowlike structures are visible in the atomic-scale STM images. A comparison with calculated STM images provides evidence that Mn atoms are incorporated into the row structures in subsurface interstitial sites, which are the lowest-energy position for Mn on Si(001). The subsurface Mn alters the height and local density of states of the Si dimer atoms, causing them to appear $0.6\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ higher than a neighboring Si dimer with no Mn below. This height difference that allows the detection the subsurface Mn results from a subtle interplay of geometrical and electronic effects.
Highlights
In recent years, several aspects of the interaction of manganese atoms with silicon surfaces have attracted attention
After in situ annealing between 300 and 700 ° C, most of the Mn is incorporated into three-dimensional manganese silicide islands, and Si dimer rows reappear in the STM images on most of the substrate surface
A comparison with calculated STM images provides evidence that Mn atoms are incorporated into the row structures in subsurface interstitial sites, which are the lowest-energy position for Mn on Si001͒
Summary
Several aspects of the interaction of manganese atoms with silicon surfaces have attracted attention. It has been speculated that incorporation of Mn on substitutional sites of the Si lattice using nonequilibrium growth techniques could turn silicon into a dilute magnetic semiconductor, similar to Mn incorporation in Ge, or could be used to achieve ␦ doping of Si with possible applications as spin valves.. An alternative route to spintronics applications focuses on heterostructures formed by magnetic metal layers on silicon. Such heterostructures could be used as Schottky diodes for injection of a spin-polarized current, a concept that has been successfully demonstrated already for nonmagnetic tunnel contacts.. Theoretical considerations suggest that epitaxial MnSi thin films should order ferromagnetically on Si001͒.7. This has lead to the expectation that MnSi films on Si could be used to fabricate magnetic heterostructures by molecular-beam epitaxy Such heterostructures could be used as Schottky diodes for injection of a spin-polarized current, a concept that has been successfully demonstrated already for nonmagnetic tunnel contacts. Theoretical considerations suggest that epitaxial MnSi thin films should order ferromagnetically on Si001͒.7 This has lead to the expectation that MnSi films on Si could be used to fabricate magnetic heterostructures by molecular-beam epitaxy
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